Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, and orthogonal frequency division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the mobile stations, and the reverse link (or uplink) refers to the communication link from the mobile stations to the base stations. This communication link may be established via a single-in-single-out, multiple-in-single-out or a multiple-in-multiple-out (MIMO) system.
A user equipment (UE) (i.e., a mobile station) may need to handover from a serving evolved-Node B (eNB) (i.e., base station) to a target eNB for a plurality of reasons, such as experiencing a weak communication link between the UE and the serving eNB due to the variations in channel quality by time, leaving a cell that is serviced by an eNB and entering a new cell, etc. The handover may be controlled by the UE or by the serving eNB. If the UE initiates the handover, a UE-controlled handover is performed. If the serving eNB initiates the handover, a network-controlled handover is performed.
In LTE standard, a UE-controlled handover is used only when the communication link to the serving eNB is in failure. The UE-controlled handover in LTE has a few drawbacks, such as large service interruption time before handover, possibility of a weak communication channel between the UE and a target eNB even after the handover, etc.
Therefore, there is a need in the art for an efficient handover mechanism from a serving eNB to a target eNB that takes into account the quality of the links between the UE and the neighboring eNBs that are candidates for the handover.